[Frequency of antibody formation during biological therapies in inflammatory bowel diseases].

Biological therapies have revolutionized the treatment of inflammatory bowel diseases enabling mucosal healing and sustained remission. However, their long-term effectiveness is substantially limited by immunogenicity, namely the development of anti-drug antibodies, which may lead to secondary loss of response. The aim of our study was to evaluate real-world immunogenicity data in Hungary among patients treated with tumor necrosis factor inhibitors infliximab (IFX) and adalimumab (ADA), as well as second-line biological agents vedolizumab (VDZ) and ustekinumab (UST). We performed a cross-sectional analysis of 153 inflammatory bowel disease patients receiving IFX or ADA and 183 patients treated with UST or VDZ, followed at Semmelweis University between 2020 and 2025. Both pediatric and adult patients were included. Immunogenicity data were assessed using modern immunoassay techniques, and results were analyzed according to treatment groups, disease characteristics, age, and sex. The overall prevalence of anti-drug antibodies was comparable between treatment groups (IFX/ADA: 21%, 32/153; UST/VDZ: 20%, 37/181; p = 0.98). In molecule-specific analyses, IFX was associated with significantly higher immunogenicity (33.0%) compared with ADA (12.0%; p = 0.001). Antibody positivity was low in patients treated with UST (15.0%), while a non-significantly higher rate was observed with VDZ (28.0%; p = 0.105). No significant differences in immunogenicity were detected according to inflammatory bowel diseases subtype, age, or sex. Although the overall immunogenicity of biological therapies may appear similar, substantial differences exist between individual agents. The higher immunogenicity of IFX compared with ADA supports the need for proactive therapeutic drug monitoring and, where appropriate, combination therapy. In the case of VDZ and UST, a more nuanced interpretation is required, considering the potential presence of transient antibodies. Our findings further emphasize the pivotal role of therapeutic drug monitoring in optimizing biological treatment strategies in inflammatory bowel diseases. Orv Hetil. 2026; 167(8): 291-299.